Compound escapement with spring mounted mass



Oct. 2, 1951 J. G. M. vm

COMPOUND ESCAPEMENT WITH SPRING MOUNTED MASS Filed March 19, 1949 Fig.4.

EFFECT/V5 FOHCE 0/? CURRA'NT RANGE APPZ /D FORGE OF? CURRENT Inverwtor:John G. MrVibi,

Hi8 Attorney.

Patented Oct. 2, 1951 COMPOUND ESCAPEMENT WITH SPRING MOUNTED MASS JohnG. M. Viti, Philadelphia, Pa., assignor to General Electric Company, acorporation of New York Application March 19, 1949, Serial No. 82,468

-My invention relates to an improvement in escapement mechanisms, andmore particularly to an escapement device used for producing a variableretarding effect. The invention may be utilized especially in connectionwith a delayedaction circuit breaker and provides a time delay which ismore variable in accordance with the degree of overcurrent passingthrough the breaker than is the case with conventional escapementmechanisms.

The use of escapement devices to regulate or retard motion is wellknown. The anchor type of escapement is particularly well known.

The conventional anchor escapement is comprised of a centrally-pivotedbody or pallet having projections at each end which engage the teeth ofan adjacent ratchet or escapement Wheel. As the escapement wheelrotates, the pallet oscillates about its pivot as its end projectionsmesh into and out of the ratchet teeth. Due to its engagement with theoscillating pallet, a retarding action is produced on the escapementwheel, the degree of retardation being a function of the inertia of thepallet and that of any mass connected rigidly thereto.

A limitation of the conventional anchor escapement which may proveundesirable in certain applications is that with any given mass whichthe pallet member may have, the escape ment wheel will be restrained inaccordance with what might be termed a natural force-time.

characteristic, the time or delay having an inverse relationship to theturning force or moment applied at the ratchet wheel. In cases where theapplied force is always the same, the retard- L ing time or delayingaction also will not vary. Such is the case, for example, in theconventional timer mechanism employed for regulating the reclosing delayof a circuit recloser as set forth in U. S. Patent 2,069,082 to Wallewhich is assigned to the same assignee as the present application. Whereautomatic circuit reclosers of this type are used, say, on a coordinatedcascade rural distribution system, it is usual to employ pallet weightsof different masses for reclosers of different current or interruptingcapacity, those for the smaller ratings having heavier timer weights sothat they operate with a longer reclosing time than the reclosers ofhigher amperage rating nearer to the power source. It will be clear,then, that increasing the effective pallet mass will increase theretarding effect or increase the time delay. Thus, if it were possibleto vary the pallet mass automatically in accordance with the appliedforce, it will be apparent that a vari 1 Claim. (Cl. 74--1.5)

able force-time characteristic wouldbeobtained.

in contra-distinction to that of the natural one defined hereinbefore.In accordance with my invention, I achieve a variable force-timecharacteristic by articulate.

ing, with spring means, the mass of (or the mass associated with) thepallet of an escapement timer mechanism, as will be more clearlyexplained hereinafter.

When a timer mechanism is required to provide a time-delay opening for,say, a reclosing circuit breaker, it is desirable that the time-delayforce-time characteristic be variable rather than natural; that is, theinterrupting contacts preferably should open considerably faster forheavy overload currents than would be the case with a timer mechanismoperating with a natural current-time characteristic.

This is particularly desirable when the power circuit which the recloseror breaker interrupts is provided with appropriate protective fuses, as

the time required for the fuses to open depends on the over-currentmagnitude, and therefore the time required for the breaker to openshould also be related to the over-current magnitude,

instead of due to rare excessive overloads, as is the intended functionof the fuse.

On the other hand, it often is desirable that the breaker open with atleast some predetermined brief delay so that the fault is given anopportunity to clear itself. Because the currenttime characteristics ofcoordinated fuses in a cascaded system lie along a steeper plotted curvethan the natural force-time characteristic of a conventional timermechanism, it is desirable to provide a timer having an appropriatevariable force-time characteristic.

It is, therefore, an object of my invention to 7 provide an escapementmechanism which will automatically modify its retarding effect to followa variable force-time characteristic in accordance with the forceavailable from the device being controlled.

It is a further object of my invention to provide.

9.21 escapement timer device which in effect operates with a variableinertia reaction in its response to externally applied forces.

It is a still further object of my invention to provide an escapementdevice which will variably retard the opening or closing of a circuitbreaker, in accordance with predetermined requirements of somecontrolling condition, such as degree of over-current.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawings and its scope will bepointed out in the appended claim.

In the drawings, Fig. 1 shows an escapement embodying my inventioncomprising an oscillating pallet with its associated spring-mountedmass, cooperating with an escapement wheel.

Fig. 2 shows an end view of the pallet, springmounted mass andescapement wheel of Fig. 1.

Fig. 3 shows the pallet and spring-mounted massof Fig. l as part of anoperating mecha nism which provides a variable time delay opening for acircuit interrupter.

Fig. 4 is a graphic comparison between the time delays provided by theconventional escapement mechanisms and the escapement of this invention.

Referring now to the drawings, Fig. 1 shows an embodiment of thearticulated-mass pallet of my invention, cooperating with an-escapementwheel. As will be seen from the drawing, the oscillating escapementassembly i consists of a light-weight pallet member 2 and a superposedmass 3, both pivotally mounted on the same pin -l, and havingappropriate springs 5 disposed between the pallet and mass. Mass 3 isprovided with two recesses 6 and 7 into which springs 5 are placed. Wheninserted therein, these springs extend beyond the recesses 6 and I so asto abut against the inside surfaces of pallet projections 8. projections8 of pallet member 2 mesh with the teeth of escapement wheel 9.

As shown in Fig. 2, pallet member 2 has two sides H], II which arespaced apart a sufficient distance to permit mass 3 to fit between themwith suitable working clearance. The sides II are connected to eachother at their ends where the pallet teeth or projections 8 constitute abridge across the space between the two sides.

When escapement wheel 9 is driven due to some comparatively lowexternallyapplied"mo ment, it will move so slowly as to'cause the entirepallet assembly I, consisting of pallet memher 2, mass 3' and interposedsprings 5, to oscillate as a single unit about pivot Because the springs5 are selected so as to have strength enough to overcome low inertiaforces of the mass" 3, they will transmit the movement of the pallet 2tothe mass 3 so that at slow speeds these'three elements, pallet,springs, and mass, will move together substantially in phase as a solidmember.

If now a somewhat larger driving force is ap-- plied, the speed ofrotation of escapement wheel 9"will increase and the oscillations ofmass 3 will become less pronounced, due to the inability of therelatively light springs 5 to transmit enough force to preponderate overthe inertia of the mass although pallet 2 will be oscill-ating'rapidly.In-

this extreme condition, it will be appreciated that It will thus bediscerned that a 4 (neglecting the mass of the light springs 5) theretardation or delay effect will be due to that of the inertia of thepallet 2 alone, so that the mass 3 may be regarded as being virtuallynonexistent.

Thus, the oscillatory characteristics of the escapement assembly I doesnot depend solely on one mass as doesthe conventional anchor escapement.Instead, the total mass may be split into plural parts, pallet 2 andmass 3, which acts as one mass at lower speeds, and as two masses athigher speeds, one of which, mass 3, becomes ineffective at higherspeeds in so far as retardation effect is concerned. While I have shownthe pallet mass articulated into two spring-connected components, itwill be apparent that I can subdivide" it into a greater number ofspring-connected plural mass components.

Fig. 3 shows schematically an application of the escapement device ofthis invention to a timedelay opening mechanism for a circuit breaker.-

Assuming that an overload exists on the circuit,-

an excess amount of current will pass through solenoid [2 which is inseries with one of the power lines. This excess current will besufficient to cause armature or core l3 to be pulled up into' thesolenoid. However, the motion of the core will be delayed by means ofthe escapement device as follows: One end of the shaft or rod ['4' towhich core [3 is attached is provided with ratchet teeth l5 which engageratchet wheel l6.-

Due to the use ofescapement device I, the

speed with which rod I4 is permitted to move upwardly so as to openswitch [9 varies greatly with the degree of overload on the circuit. Onthe other hand, if a conventional anchor type escapement were used, theamount of time delay before opening the circuit would not have nearlythe flexibility provided with this invention.

The performance of my articulated mass palletmay be compared best withthat of the former solid mass pallet escapement mechanisms by re--ferring to Fig. 4 which graphically illustrates by curves the force-timecharacteristics involved.

The several curves are represented as commencing and terminating withinthe force or current range over which the respective escapements areeffective. plot of the natural force-time characteristic of aconventional escapement employing a relatively heavy mass fixed to thepallet. If a light mass pallet be substituted for a heavy mass palletthe resulting plot would produce a curve similarto the first but lyinggenerally at a lower level (shorter time) as represented by the dottedcurve I Assuming now that the desired force-time" characteristic of thefuses with which it is desired to coordinate the breaker lie along asteeper plot,

say, from A to b, Ican fulfill this requirement by the properselectionof pallet weight, springstrength, and weight'of the-superposedmass. To'

this end, ifthepallet'weight is made equal The dotted curve AB is a massto the light-weight pallet mass which produces the curve ab, and anarticulated springconnected mass is applied thereto such that thesummation of the mass and pallet is the equivalent of that of the heavysolid-mass pallet which produced curve AB, then, in accordance with theexplanation already set forth, it will be understood that a plot of theresulting variable force-time characteristic curve will conform somewhatto the full line curve Ab on the diagram. In other words, and as borneout by tests on samples of my device, the variable force-timecharacteristic of the articulated mass pallet will generally conform atone end of its range to that of the heavy mass pallet curve AB, and willalso generally conform to that of the light-Weight mass at the other endof the range as at b. Intervening points between A and b on this curvewill follow a plot representation which will conform more or less to thegradual transition repesented by the full line curve Ab having thedesired steeper slope which is unattainable through the agency of theformer fixed. mass pallet design.

From the above explanation, it will be perceived that I can achieve evengreater variability by employing a still heavier combined springconnected mass, in which case the full line curve would commence at somepoint higher than A; and if the pallet mass alone were madecorrespondingly lighter, the right hand end of the curve would then lieat some point lower than that indicated by b. If the total mass isubdivided into more than two spring-divided articulated elements, it isexpected that the path or transition from the higher end to the lower ofthe effective range Ab would follow a more uniform or predictablepattern.

Thus it will be seen that I have provided means for producing a"variable force-time characteristic which more nearly conforms to thatof a series of cascaded protective fuses than has been possible hithertoby means of the fixedmass conventional escapement devices of the priorart.

While there have been shown and described particular embodiments of myinvention, it will be obvious to those skilled in the art that variouschanges and modifications can be made therein without departing from theinvention and, therefore, it is aimed in the appended claim to cover allsuch changes and modifications as fall within the true spirit and scopeof the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

A time delay means comprising a toothed escape wheel, a centrallypivoted pallet member having projections at its opposite ends adapted toengage the teeth of said escape wheel, said pallet member oscillatingabout its pivot as said escape wheel rotates, a mass member, theinterior of said pallet member being recessed to receive said massmember, said mass member being centrally pivoted about the same axis ofoscillation as said pallet member, and spiral spring members interposedbetween said pallet member and said mass member on either side of saidaxis of oscillation for transmitting oscillatory force between saidmembers.

JOHN G. M. VITI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,918,378 Burnham July 18, 19332,069,082 Walle Jan. 26, 1937 2,362,836 McCullough Nov. 14, 19442,364,143 Horton et a1. Dec. 5, 1944 2,464,303 Gesellschap Mar. 15, 1949FOREIGN PATENTS Number Country Date 11,032A Great Britain May 10, 1890287,844 Germany Oct. 10, 1913 558,322 Great Britain Dec. 31, 1943

